U.S. patent application number 14/909996 was filed with the patent office on 2016-06-23 for production of organic phosphorescent layers with addition of heavy main group metal complexes.
This patent application is currently assigned to Siemens Aktiengesellschaft. The applicant listed for this patent is SIEMENS AKTIENGESELLSCHAFT. Invention is credited to Florian Kessler, Ana-Maria Krestel, Anna Maltenberger, Guenter Schmid, Dan Taroata.
Application Number | 20160181540 14/909996 |
Document ID | / |
Family ID | 50732145 |
Filed Date | 2016-06-23 |
United States Patent
Application |
20160181540 |
Kind Code |
A1 |
Kessler; Florian ; et
al. |
June 23, 2016 |
Production Of Organic Phosphorescent Layers With Addition Of Heavy
Main Group Metal Complexes
Abstract
A method is provided for producing organic electrical layers
having organic emitters that are phosphorescent at room
temperature. Organic fluorescent emitters, together with organic
complex ligands containing metal complexes, and at least one heavy
main group metal, selected from the group comprising In, Tl, Sn,
Pb, Sb and Bi, are deposited jointly inside a layer, and the heavy
main group metal changes its coordination sphere by receiving the
organic fluorescent emitter.
Inventors: |
Kessler; Florian;
(Hoechstadt an der Aisch, DE) ; Krestel; Ana-Maria;
(Erlangen, DE) ; Maltenberger; Anna; (Leutenbach,
DE) ; Schmid; Guenter; (Hemhofen, DE) ;
Taroata; Dan; (Erlangen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SIEMENS AKTIENGESELLSCHAFT |
Munchen |
|
DE |
|
|
Assignee: |
Siemens Aktiengesellschaft
Muenchen
DE
|
Family ID: |
50732145 |
Appl. No.: |
14/909996 |
Filed: |
May 8, 2014 |
PCT Filed: |
May 8, 2014 |
PCT NO: |
PCT/EP2014/059463 |
371 Date: |
February 4, 2016 |
Current U.S.
Class: |
257/40 ;
252/301.16; 438/46 |
Current CPC
Class: |
H01L 51/0077 20130101;
C09K 2211/1029 20130101; C09K 11/06 20130101; H01L 51/5016
20130101; H01L 51/0072 20130101; C09K 2211/1007 20130101; C09K
2211/188 20130101; Y02E 10/549 20130101; H01L 51/0051 20130101;
C09K 2211/1044 20130101; H01L 51/56 20130101 |
International
Class: |
H01L 51/00 20060101
H01L051/00; C09K 11/06 20060101 C09K011/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2013 |
DE |
10 2013 215 342.2 |
Claims
1. A process for producing organic electronic layers including
organic emitters that are phosphorescent at room temperature, the
process comprising: providing organic fluorescent emitters,
providing metal complexes containing organic complex ligands,
providing at least one heavy main group metal selected from the
group consisting of In, Tl, Sn, Pb, Sb and Bi within one layer, and
codepositing the organic fluorescent emitters together with the
metal complexes containing organic complex ligands and the at least
one heavy main group metal on a substrate, wherein the heavy main
group metal alters its coordination sphere in response to being
combined with the organic fluorescent emitters.
2. The process of claim 1, wherein the heavy main group metal
comprises Bi.
3. The process of claim 1, wherein the organic electronic layers
exhibit a proportion of phosphorescent emission caused by
electronic inter- and intra-ligand transfers with purely electronic
excitation of not less than 20% and not more than 100%.
4. The process of claim 1, wherein the organic fluorescent emitters
comprise substituted or unsubstituted C6-C60 aromatics or
heteroaromatics.
5. The process of claim 1, wherein the organic fluorescent emitter
is 4,7-di(9H-carbazol-9-yl)-1,10-phenanthroline (BUPH1).
6. The process of claim 1, wherein the ligands of the metal complex
are independently selected from the group consisting of (a) halides
and (b) fluorinated or nonfluorinated C2-C20 alkyl or aryl
carboxylates, alkoxides, thiolates, cyanates, isocyanates,
thiocyanates, acetylacetonates, or sulfonates.
7. The process of claim 1, wherein the metal complex comprises one
or more compounds selected from the group consisting of Bi(III)
fluorobenzoate, Bi(III) fluoroalkyl-benzoate, Bi(III)
fluorodialkylbenzoate, Bi(III) fluorotri-alkylbenzoate, Bi(III)
pentafluorobenzoate, and Bi(III) 3,5-trifluoromethylbenzoate.
8. The process of claim 1, wherein the metal complex comprises one
or more triarylbismuth(V) carboxylates.
9. The process of claim 1, wherein the metal complex comprises
Bi(III) triscarboxylate, Bi(III) fluoroacetate, or Bi(III)
trifluoroacetate.
10. The process of claim 1, comprising depositing the metal complex
and the organic fluorescent emitter on a carrier substrate by
coevaporation, rotary or curtain coating, bar coating, or
printing.
11. The process of claim 10, wherein the organic electronic layers
have a molar ratio of metal complex to organic fluorescent emitter
F of not less than 1:10 and not more than 10:1.
12. The process of claim 10, comprising depositing the metal
complex and the organic fluorescent emitter using a coevaporation
process with a deposition rate of the organic electronic layer of
not less than 0.1 .ANG./s and not more than 200 .ANG./s.
13. A layer in an organic electronic component produced by a
process comprising: providing organic fluorescent emitters,
providing metal complexes containing organic complex ligands,
providing at least one heavy main group metal selected from the
group consisting of In, Tl, Sn, Pb, Sb and Bi within one layer, and
codepositing the organic fluorescent emitters together with the
metal complexes containing organic complex ligands and the at least
one heavy main group metal, wherein the heavy main group metal
alters its coordination sphere in response to being combined with
the organic fluorescent emitters.
14. (canceled)
15. An organic semiconductor component comprising: at least one
layer produced by a process comprising: providing organic
fluorescent emitters, providing metal complexes containing organic
complex ligands, providing at least one heavy main group metal
selected from the group consisting of In, Tl, Sn, Pb, Sb and Bi
within one layer, and codepositing the organic fluorescent emitters
together with the metal complexes containing organic complex
ligands and the at least one heavy main group metal, wherein the
heavy main group metal alters its coordination sphere in response
to being combined with the organic fluorescent emitters.
16. The organic semiconductor component of claim 15, wherein the
organic semiconductor component comprises a photodiode, a solar
cell, an organic light-emitting diode, or a light-emitting
electrochemical cell.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. National Stage Application of
International Application No. PCT/EP2014/059463 filed May 8, 2014,
which designates the United States of America, and claims priority
to DE Application No. 10 2013 215 342.2 filed Aug. 5, 2013, the
contents of which are hereby incorporated by reference in their
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a process for producing
organic electronic layers including organic emitters that are
phosphorescent at room temperature, wherein organic fluorescent
emitters F are codeposited together with metal complexes containing
organic complex ligands L and at least one heavy main group metal M
selected from the group comprising In, Tl, Sn, Pb, Sb and Bi within
one layer and the heavy main group metal M alters its coordination
sphere with incorporation of the organic fluorescent emitter F.
BACKGROUND
[0003] Methods in principle for conversion of light to electrical
current (and vice versa) by means of organic electronics have been
known for several decades. An industrial breakthrough has been
accomplished by multilayer constructions which are currently on the
point of readiness for the mass market, as shown schematically, for
example, in figure I for an organic light-emitting diode (OLED) or
in figure II for an organic solar cell. Even though the efficiency
of these components in the last few years in particular has
undergone a distinct rise in performance through the use of
optimized classes of organic compounds, promising approaches are
still resulting in even higher quantum yields and hence even higher
efficiencies with lower material costs.
[0004] One of these approaches lies in the use of phosphorescent
emitters, called triplet emitters, which find use, for example, in
PHOLEDs (phosphorescent organic light-emitting devices). In view of
the applicable quantum statistics, these are at least theoretically
capable of achieving an internal quantum efficiency of 100%. This
contrasts with diodes having purely fluorescent emitters which, on
the basis of the quantum statistics of the injected charge
carriers, have a maximum internal quantum yield of only 25%.
[0005] Considering the internal quantum yield alone, organic
electronic components which utilize a phosphorescence-based
conversion of current to light (and vice versa) (triplet
emitter/emission) are thus more suitable for providing a high
luminescence (cd/m.sup.2) or efficiency (cd/A, lm/W). Within the
field of compounds capable of triplet emission, however, several
boundary conditions have to be observed. Although phosphorescence
also occurs in compounds of the elements of the fourth and fifth
periods of the Periodic Table, it is the complexes of the metals of
the 6th period that have become established in the abovementioned
applications. According to the position of the elements in this
period, the origin of the phosphorescence is weighted differently
within the orbital structure of the complexes.
[0006] In the case of the lanthanoids, both the HOMO (Highest
Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied
Molecular Orbital) are predominantly metal-centered, meaning that
the proportion of the ligand orbitals is relatively minor. The
effect of this is that the emission wavelength (color) of the
emitters is determined almost exclusively by the band structure of
the metal (examples: europium=red, terbium=green). Because of the
strong shielding of the f electrons of these metals, ligands
coupled to the metal are able to split the energies of the f.sup.n
configuration of the metals only by about 100 cm.sup.-1, such that
there is a considerable difference in the spectroscopy, by virtue
of their ligand field, of the d ions from that of the f ions. In
the case of ions of the lanthanides, the color results from
transitions from f to unoccupied s, p and d orbitals.
[0007] Going along the period to the elements of osmium, iridium,
platinum and gold, ligand fields split the metal orbitals by a
factor of 10-100 times more than in the case of the lanthanoids. It
is thus possible to represent virtually the entire wavelength
spectrum by varying the ligands with these elements. The strong
coupling of the spin angular momentum of the metal atom with the
spin angular momentum of the electrons results in phosphorescence
being obtained in the emitters. The HOMO is usually metal-centered,
while the LUMO is usually ligand-centered. The radiative
transitions are therefore referred to as metal-ligand charge
transfer transitions (MLCT).
[0008] Both OLEDs and OLEECs (light-emitting organic
electrochemical cells) currently utilize almost exclusively iridium
complexes as emitters. In the case of the OLEDs, the emitter
complexes are uncharged; in the case of the OLEECs, ionic, i.e.
charged, emitter complexes are utilized. However, the use of
iridium in these components has a serious disadvantage. The annual
production of iridium is well below 10 t (3 t in 2000). The effect
of this is that the material costs make a significant contribution
to the production costs of organic electrical components. An
additional factor is that iridium emitters are incapable of
efficiently representing the entire spectrum of visible light. For
example, stable blue iridium emitters are comparatively rare, which
is a barrier to flexible use of these materials in OLEDs or
OLEECs.
[0009] In the recent literature, however, there are some approaches
which propose "triplet harvesting" even with non-iridium-based
emitters. For example, Omary et al. in "Enhancement of the
Phosphorescence of Organic Luminophores upon interaction with a
Mercury Trifunctional Lewis Acid" (Mohammad A. Omary, Refaie M.
Kassab, Mason R. Haneline, O. Elbjeirami, and Francois P. Gabbai,
Inorg. Chem. 2003, 42, 2176-2178) point out the possibility of
achieving adequate phosphorescence of purely organic emitters
through the use of mercury. As a result of the heavy atom effect of
mercury in a matrix composed of organic ligands, a
singlet-triplet/triplet-singlet transition of the excited electrons
in the organic matrix is enabled by quantum-mechanical means (ISC,
intersystem crossing), which results in a distinct reduction in the
lifetime of the excited electronic (triplet) states and prevents
unwanted saturation of the population of these states. The cause of
this mechanism is the spin-orbit coupling of the heavy mercury atom
with the excited electrons of the organic matrix. A disadvantage,
however, is that the use of mercury is problematic for reasons of
toxicology and environmental policy.
[0010] One means of obtaining an adequate quantum yield on the
basis of purely organic phosphorescence emitters is described, for
example, by Bolton et al. in NATURE CHEMISTRY, 2011, 1-6
("Activating efficient phosphorescence from purely organic
materials by crystal design", Onas Bolton, Kangwon Lee, Hyong-Jun
Kim, Kevin Y. Lin and Jinsang Kim, NATURE CHEMISTRY, 2011, 1-6).
This article suggests that the incorporation of heavy halides into
a crystal composed of an organic matrix leads to high quantum
yields through phosphorescent organic emitters. However, a
disadvantage of this solution is that a particular distance between
the heavy halides and the organic matrix and a crystalline
structure seem to be necessary for this effect. This would be a
barrier to inexpensive industrial manufacture of organic
components.
[0011] WO 2012/016074 A1, by contrast, describes a thin layer
comprising a compound of the formula
##STR00001##
where Ar.sup.1 and Ar.sup.2 are each independently a C3-C30
aromatic ring; R.sup.1 and R.sup.2 are a substituent; a and b are
each independently an integer from 0 to 12, where, when a is 2 or
more, each R.sup.1 radical is optionally different from the others,
and two R.sup.1 radicals are optionally bonded to one another to
form a ring structure, and, when b is 2 or more, each R.sup.2
radical is optionally different from the others, and two R.sup.2
radicals are optionally bonded to one another to form a ring
structure; A.sup.1 is any kind of direct bond, --O--, --S--,
--S(.dbd.O)--, --S(.dbd.O).sub.2--, --PR.sup.3--, --NR.sup.4-- and
--C(R.sup.5).sub.2--; R.sup.3 is a hydrogen atom or a substituent;
R.sup.4 is a hydrogen atom or a substituent; R.sup.5 is a hydrogen
atom or a substituent and two R.sup.5 radicals are optionally
different from one another; E.sup.1 is a monovalent radical having
50 or fewer carbon atoms; L.sup.1 is a ligand having 50 or fewer
carbon atoms; c is an integer from 0 to 3, where, when c is 2 or
more, each L.sup.1 radical is optionally different from the others;
and every combination of a combination of E.sup.1 and Ar.sup.1 and
a combination of E.sup.1 and Ar.sup.2 optionally forms a bond; and,
when c is 1 to 3, every combination of a combination of L.sup.1 and
E.sup.1, a combination of L.sup.1 and Ar.sup.1, a combination of
L.sup.1 and Ar.sup.2 and a combination of L.sup.1 and L.sup.1
optionally forms a bond. A disadvantage, however, is that the
compounds described have only an inadequate quantum yield and are
insufficiently stable in solution, such that they decompose.
[0012] DE 103 60 681 A1 discloses main group metal diketonato
complexes according to the following formula:
##STR00002##
as phosphorescent emitter molecules in organic light-emitting
diodes (OLEDs) in which M may be Tl(I), Pb(II) and Bi(III).
Additionally disclosed is the use of these main group metal
diketonato complexes as light-emitting layers in OLEDs,
light-emitting layers comprising at least one main group metal
diketonato complex, an OLED comprising this light-emitting layer,
and devices comprising an OLED of the invention. In experiments,
however, it was shown that the abovementioned compounds synthesized
with strict exclusion of water do not exhibit phosphorescence-based
emission after electronic excitation. It is highly likely that the
phosphorescent emissions cited originate from indeterminate oxo
clusters which have formed in an uncontrolled manner, for example
as a result of hydrolysis in the course of preparation. A
disadvantage of this specific solution is that the n system of
these acetylacetonate ligands, especially of the fully fluorinated
variants described, is not very well-developed and, as a sole
phosphorescent emitter, allows only small phosphorescence
yields.
SUMMARY
[0013] One embodiment provides a process for producing organic
electronic layers including organic emitters that are
phosphorescent at room temperature, wherein organic fluorescent
emitters F are codeposited together with metal complexes containing
organic complex ligands L and at least one heavy main group metal M
selected from the group comprising In, Tl, Sn, Pb, Sb and Bi within
one layer and the heavy main group metal M alters its coordination
sphere with incorporation of the organic fluorescent emitter F.
[0014] In a further embodiment, the heavy main group metal
comprises Bi.
[0015] In a further embodiment, the proportion of phosphorescent
emission caused by electronic inter- and intra-ligand transfers
with purely electronic excitation is not less than 20% and not more
than 100%.
[0016] In a further embodiment, the organic fluorescent emitters F
are selected from the group of the substituted or unsubstituted
C6-C60 aromatics or heteroaromatics.
[0017] In a further embodiment, the organic fluorescent emitter F
is 4,7-di(9H-carbazol-9-yl)-1,10-phenanthroline (BUPH1).
[0018] In a further embodiment, the ligands L of the metal complex
are independently selected from the group comprising halides and
fluorinated or nonfluorinated C2-C20 alkyl or aryl carboxylates,
alkoxides, thiolates, cyanates, isocyanates, thiocyanates,
acetylacetonates, sulfonates.
[0019] In a further embodiment, the metal complex comprises one or
more compounds from the group of Bi(III) fluorobenzoate, Bi(III)
fluoroalkyl-benzoate, Bi(III) fluorodialkylbenzoate, Bi(III)
fluorotri-alkylbenzoate, Bi(III) pentafluorobenzoate and Bi(III)
3,5-trifluoromethylbenzoate.
[0020] In a further embodiment, the metal complex comprises one or
more compounds from the group of the triarylbismuth(V)
carboxylates.
[0021] In a further embodiment, the metal complex is selected from
the group comprising Bi(III) triscarboxylate, Bi(III) fluoroacetate
and Bi(III) trifluoroacetate.
[0022] In a further embodiment, the metal complex and the organic
fluorescent emitter F are deposited on a carrier substrate by means
of coevaporation, rotary or curtain coating, bar coating or
printing.
[0023] In a further embodiment, the molar ratio of metal complex to
organic fluorescent emitter F is not less than 1:10 and not more
than 10:1.
[0024] In a further embodiment, the deposition of the metal complex
and the organic fluorescent emitter F is effected by means of a
coevaporation method and the deposition rate of the organic
electronic layer is not less than 0.1 .ANG./s and not more than 200
.ANG./s.
[0025] Another embodiment provides a layer in an organic electronic
component produced by any of the processes disclosed above.
[0026] Another embodiment provides a use of a layer as disclosed
above as an active layer in an organic electronic component for
conversion of electrical current to light, of light to electrical
current and of light to light of another wavelength.
[0027] Another embodiment provides an organic semiconductor
component selected from the group comprising photodiodes, solar
cells, organic light-emitting diodes, light-emitting
electrochemical cells comprising a layer as disclosed above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Example embodiments of the invention are discussed in detail
below with reference to the drawings, in which:
[0029] FIG. 1 shows a schematic of the structure of an organic
light-emitting diode 10. The light-emitting diode is constructed
from a glass layer 1; indium tin oxide ITO layer 2; hole injector
layer 3; hole transport layer HTL 4; emitter layer EML 5; hole
blocker layer HBL 6; electron transport layer ETL 7; electron
injector layer 8 and a cathode layer 9;
[0030] FIG. 2 shows a schematic of the structure of an organic
solar cell having PIN structure 20 which converts light 21 to
electrical current. The solar cell consists of a layer of indium
tin oxide 22; a p-doped layer 23; an absorption layer 24; an
n-doped layer 25 and a metal layer 26;
[0031] FIG. 3 shows the photoluminescence spectra of solid and
THF-dissolved BUPH1 at room temperature;
[0032] FIG. 4 shows the photoluminescence spectra of BUPH1 in
2-methyl-THF at 77 K;
[0033] FIG. 5 shows the time-correlated single photon counting
(TCSPC) spectrum of BUPH1 in THF for determination of the
fluorescence lifetime of BUPH1;
[0034] FIG. 6 shows the cyclic voltammogram of BUPH1 in
acetonitrile;
[0035] FIG. 7 shows the UV absorption spectra of Bi(tfa).sub.3,
Bi(pFBz).sub.3 and Bi(3,5tfmBz).sub.3 together with a Tauc
diagram;
[0036] FIG. 8 shows the plot of the molar extinction coefficients
of Bi(tfa).sub.3, Bi(pFBz).sub.3 and Bi(3,5tfmBz).sub.3 in THF
against wavelength;
[0037] FIG. 9 shows the UV absorption spectra of BUPH1,
Bi(tfa).sub.3 and Bi(tfa).sub.3:BUPH1 layers produced by
coevaporation at different deposition rates;
[0038] FIG. 10 shows the UV absorption spectra of BUPH1 and
Bi(pFBz).sub.3:BUPH1 layers produced by coevaporation at different
deposition rates;
[0039] FIG. 11 shows the normalized photoluminescence spectrum of
BUPH1 and Bi(tfa).sub.3:BUPH1 layers produced by coevaporation at
different deposition rates;
[0040] FIG. 12 shows the normalized photoluminescence spectrum of
BUPH1 and Bi(pFBz).sub.3:BUPH1 layers produced by coevaporation at
different deposition rates;
[0041] FIG. 13 shows the XRD spectrum of a Bi(tfa).sub.3:BUPH1
(1:1) film;
[0042] FIG. 14 shows the UV absorption spectra in the range between
250 and 475 nm of SnCl.sub.2-BUPH1 adducts or complexes with
different composition. What are shown are the UV absorption spectra
of 1:1, 1:2 and 1:3 adducts or complexes in THF at room
temperature;
[0043] FIG. 15 shows the UV absorption spectra in the range between
350 and 475 nm of SnCl.sub.2-BUPH1 adducts or complexes with
different composition. What are shown are the UV absorption spectra
of 1:1, 1:2 and 1:3 adducts or complexes in THF at room
temperature. The data correspond to the results from FIG. 14 and
are merely enlarged and shown in sections;
[0044] FIG. 16 shows the normalized photoluminescence spectrum of
SnCl.sub.2-BUPH1 adducts or complexes with different composition
(1:1, 1:2 and 1:3) in THF at room temperature. The excitation
wavelength was 410 nm.
[0045] FIG. 17 shows the time-correlated single photon counting
(TCSPC) spectrum of 1:1 SnCl.sub.2-BUPH1 adducts or complexes in
THF at room temperature. Additionally shown is the mathematical
fit;
[0046] FIG. 18 shows the time-correlated single photon counting
(TCSPC) spectrum of 1:2 SnCl.sub.2-BUPH1 adducts or complexes in
THF at room temperature. Additionally shown is the mathematical
fit;
[0047] FIG. 19 shows the time-correlated single photon counting
(TCSPC) spectrum of 1:3 SnCl.sub.2-BUPH1 adducts or complexes in
THF at room temperature. Additionally shown is the mathematical
fit;
[0048] FIG. 20 shows the UV absorption spectra in the range between
250 and 475 nm of PbTFA-BUPH1 adducts or complexes with different
composition. What are shown are the UV absorption spectra of 1:1,
1:2 and 1:3 adducts or complexes in THF at room temperature;
[0049] FIG. 21 shows the UV absorption spectra in the range between
350 and 430 nm of PbTFA-BUPH1 adducts or complexes with different
composition. What are shown are the UV absorption spectra of 1:1,
1:2 and 1:3 adducts or complexes in THF at room temperature. The
data correspond to the results from FIG. 20 and are merely enlarged
and shown in sections.
[0050] FIG. 22 shows the normalized photoluminescence spectrum of
PbTFA-BUPH1 adducts or complexes with different composition (1:1,
1:2 and 1:3) in THF at room temperature. The excitation wavelength
was 410 nm.
[0051] FIG. 23 shows the time-correlated single photon counting
(TCSPC) spectrum of 1:1 PbTFA-BUPH1 adducts or complexes in THF at
room temperature. Additionally shown is the mathematical fit;
[0052] FIG. 24 shows the time-correlated single photon counting
(TCSPC) spectrum of 1:2 PbTFA-BUPH1 adducts or complexes in THF at
room temperature. Additionally shown is the mathematical fit;
[0053] FIG. 25 shows the time-correlated single photon counting
(TCSPC) spectrum of 1:3 PbTFA-BUPH1 adducts or complexes in THF at
room temperature. Additionally shown is the mathematical fit.
DETAILED DESCRIPTION
[0054] Embodiments of the present invention provide a process by
which it is possible to inexpensively produce layers for organic
electronic components which enable effective conversion of current
to light and vice versa through the utilization of
phosphorescence.
[0055] Some embodiments provide a process for producing organic
electronic layers including organic emitters that are
phosphorescent at room temperature, wherein organic fluorescent
emitters F are codeposited together with metal complexes containing
organic complex ligands L and at least one heavy main group metal M
selected from the group comprising In, Tl, Sn, Pb, Sb and Bi within
one layer and the heavy main group metal M alters its coordination
sphere with incorporation of the organic fluorescent emitter F. It
has been found that, surprisingly, by means of this process, it is
possible in a simple and inexpensive manner to obtain layers having
emitters that are phosphorescent at room temperature, which have a
high internal quantum efficiency, high luminances, rapid response
characteristics and good long-term stabilities. Because of the fact
that the phosphorescence is caused only by the organic emitters, by
modification of the ligands, especially the n system thereof, it is
additionally possible to tune the emission wavelength of the
emitters. It is especially possible to construct heteroleptic
complexes or addition compounds which enable emissions via the
orbitals of ligands/emitters of different structure. This
additionally increases the variety for preparation of purely
organic phosphorescent emitters. Without being bound by the theory,
within the process of the invention, the organic emitter capable of
fluorescence is deposited close to the heavy main group metal, with
a change in the coordination sphere of the metal. The change in the
coordination sphere of the metal may consist in an increase in the
number of coordinated ligands/emitters, in a replacement of one or
more ligands by emitters, or even in the reduction in the number of
coordinated ligands as a result of the adduct/addition/complex
formation with the emitter. This is a function of the steric and
electronic requirements of the emitters and ligands, the
coordination strength of the individual ligands and the deposition
rate and temperature in the context of the production chosen. In
the case of adduct formation or coordination of the emitter to the
heavy main group metal atom, there is no need for a .sigma. bond to
be formed between the heavy atom and the organic emitters. Weak
electrostatic and/or .pi. interactions between metal and emitter
are sufficient. However, the interaction with the heavy metal atom
can also result in alteration in the energy level of the HOMO/LUMO
of the fluorescent emitter(s). As a result of the heavy atom
effect, there may additionally be spin-orbit coupling between the
emitter electrons and the nucleus of the metal atom, the effect of
which is that hitherto spin-forbidden electronic transitions are
allowed by quantum-mechanical means. This lowers the lifetime of
the electronically excited states and hence opens up an effective
phosphorescence channel (with triplet-singlet transitions) at room
temperature. The metal does not become directly involved in the
emission; it merely provides its spin angular momentum. This
contrasts with the emission of the organic emitters without heavy
metal coordination, which is purely fluorescent at room
temperature.
[0056] The emitter layers obtained in accordance with the invention
may be neutral or ionic in nature and may thus exhibit emission
characteristics typical of OLEDs or OLECs.
[0057] An organic electronic layer in the context of the invention
is understood to mean a layer comprising organic emitters, metal
complexes containing heavy main group metals and optionally matrix
materials. The layer may also be amorphous, meaning that the
individual constituents in this layer do not have any periodic
arrangement over any great range (long-range order). More
particularly, this is not understood to mean the presence of a
single-crystal or crystalline regions having an extent of not less
than 50 nm. The compounds present in the layer, however, may have a
certain short-range order (distance and orientation) with respect
to their closest neighbors. But these areas are randomly
distributed. Within an x-ray diffractogram, obtained, for example,
by an XRD measurement (x-ray powder diffractometry), the amorphous
layer features a broad halo. It has been found that, surprisingly,
an amorphous arrangement of the regions in the layer is sufficient
to obtain an adequate phosphorescence yield. This contrasts with
experimental results which call for a very regular arrangement of a
multitude of metal atoms and emitters as a condition for the
obtaining of high phosphorescence yields.
[0058] As a result of the influence of the heavy metal, a
significant phosphorescence contribution of the organic fluorescent
emitter is obtained at room temperature. Room temperature in the
context of the invention is the temperature range from -50.degree.
C. to 150.degree. C. (the standard operating temperature range for
organic electronics). Within this temperature range, the
phosphorescent transitions of one or more fluorescent emitters
lacking influence from heavy metal atoms generally do not make any
significant contributions to the emission of purely organic
emitters.
[0059] Organic fluorescent emitters F are organic molecules which
can have either partial or overall aromatic character with
delocalized .pi. electrons. In addition, these molecules may have
heteroatoms such as N, N--R, O, S, Se, Si or metals such as Li or
Al, Ga or Zn. R in this case is an alkyl or aromatic radical. These
molecules, in solid form or in solution, after electronic
excitation, exhibit fluorescence, i.e. electronic (S1-S0)
singlet-singlet transitions. Phosphorescent transitions (T-S)
cannot be observed at room temperature because of the
quantum-mechanical exclusion rules (reversal of spin). The lifetime
of the fluorescent transitions in the organic fluorescent emitters
usable in accordance with the invention can be within a range below
100 ns without the proximity of the heavy metal atom.
[0060] Preferably, the organic fluorescent emitters F may be
C1,-C60 heteroaromatics, further preferably C15-C50
heteroaromatics. In specific applications, the oxygen- and
nitrogen-containing heteroaromatics have been found to be
particularly favorable. In addition, organic fluorescent emitters
which can be used with preference within the process of the
invention are those having a triplet state separated from the S0
state by not less than -5 eV and not more than 5 eV. With these
electronic boundary conditions, it is possible to obtain
particularly high quantum yields in the context of the process of
the invention.
[0061] In the context of the process of the invention, metal
complexes containing heavy main group metals M from the group
comprising In, Tl, Sn, Pb, Sb and Bi are used. These metal
complexes may include organic complex ligands and are preferred
particularly because of their availability, their procurement cost
and their ability to develop marked spin-orbit coupling and the
possibility of extending the coordination sphere. It is also
possible for a plurality of different metals from the
abovementioned group to be present in the metal complex usable in
accordance with the invention. This group is particularly suitable,
since the elements listed therein have a particularly high spin
angular momentum which enables effective phosphorescence
transitions in the organic emitters F. Moreover, these metals are
available in high purity at relatively low cost.
[0062] In a particular embodiment, the group may advantageously
also include Sn, Pb and Bi. These metals additionally have the
benefit of having very good processibility from solutions as
well.
[0063] Preferably, the metals can be coordinated to organic ligands
having terminal, bidentate, tridentate or heterobimetallic bridging
to the metal atom. Advantageous configurations can arise when the
coordination of the ligands to the metal atom is via two oxygen
atoms. Without being bound by the theory, these substituents, in
the course of the deposition process, can be efficiently displaced
by the organic emitters or the coordination sphere can be extended,
and hence contribute to a high phosphorescence yield. In addition,
by means of these substituents, the emission wavelength of the
phosphorescent light can be adjusted by ligand-ligand transitions.
Preferably, ligands coordinated in this way may have aromatic .pi.
systems having at least 10 carbon atoms. This can contribute to a
major broadening of the emission wavelengths in the case of
ligand-ligand transitions.
[0064] The heavy main group metal M alters its coordination sphere
with incorporation of the organic fluorescent emitter F. Without
being bound by the theory, in the process of the invention, the
organic emitter is brought close to the main group metal. There is
then a change in the arrangement of the ligands of the metal
complex. This is caused by van der Waals, coulombic, .pi.-.sigma.
or .sigma. interactions of the organic emitter with the metal. A
.sigma. interaction is not needed for development of
phosphorescence, but may also be formed. The coordination sphere of
the metal can be broadened by the proximity of the organic emitter.
There may also be substitution of an individual ligand or of
several ligands by the organic emitter. In addition, it is also
possible that the number of ligands is reduced by the change in the
coordination sphere. This results, for example, from the
displacement of one or more ligands by the incorporation of the
fluorescent organic emitter.
[0065] In addition to the metal complex and to the organic emitter,
it is possible in the context of the process of the invention for
further noncoordinating matrix materials to be deposited within the
layer. This/these matrix material(s) may, for example, affect the
electronic conductivity of the layer or generally affect the
mobility of the organic emitter or the metal complex. Suitable
matrix materials may be selected from the group of
2,2',7,7'-tetrakis(carbazol-9-yl)-9,9-spirobifluorene;
2,7-bis(carbazol-9-yl)-9,9-ditolylfluorene;
9,9-bis[4-(carbazol-9-yl)phenyl]-fluorene;
2,7-bis(carbazol-9-yl)-9,9-spirobifluorene;
1,4-bis-(triphenylsilyl)benzene; 1,3-bis(triphenylsilyl)benzene;
bis(4-N,N-diethylamino-2-methylphenyl)-4-methylphenylmethane;
2,7-bis(carbazol-9-yl)-9,9-dioctylfluorene;
4,4''-di(triphenyl-silyl)-p-terphenyl;
4,4'-di(triphenylsilyl)biphenyl; 9-(4-tert-butylphenyl)-3,
6-bis(triphenylsilyl)-9H-carbazole; 9-(4-tert-butylphenyl)-3,
6-ditrityl-9H-carbazole;
9-(4-tert-butylphenyl)-3,6-bis(9-(4-methoxyphenyl)-9H-fluoren-9-yl)-9H-ca-
rbazole; 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine;
3,5-bis(3-(9H-carbazol-9-yl)phenyl)pyridine,
triphenyl(4-(9-phenyl-9H-fluoren-9-yl)phenyl)silane;
9,9-dimethyl-N,N-diphenyl-7-(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-
-9H-fluoren-2-amine; 3,5-bis(3-(9H-carbazol-9-yl)phenyl)pyridine;
9,9-spirobi-fluoren-2-yldiphenylphosphine oxide; 9,
9'-(5-(triphenylsilyl)-1,3-phenylene)bis(9H-carbazole);
4,4,8,8,-12,12-hexa-p-tolyl-4H-8H-12H-12C-azadibenzo[cd,mn]pyrene;
2,2'-bis(4-(carbazol-9-yl)phenyl)biphenyl;
2,8-bis(diphenylphosphoryl)dibenzo[b,d]-thiophene;
bis(2-methylphenyl)diphenylsilane;
bis[3,5-di(9H-carbazol-9-yl)phenyl]diphenylsilane;
3,6-bis(carbazol-9-yl)-9-(2-ethylhexyl)-9H-carbazole;
3-(diphenylphosphoryl)-9-(4-(diphenylphosphoryl)phenyl)-9H-carbazole;
3,6-bis[(3,5-diphenyl)phenyl]-9-phenylcarbazole;
2,8-di(9H-carbazol-9-yl)-dibenzo[b,d]thiophene;
10-(4'-(diphenylamino)biphenyl-4-yl)-acridin-9(10H)-one;
2,7-bis(diphenylphosphoryl)-9,9'-spiro-bi[fluorene];
1,4-bis((9H-carbazol-9-yl)methyl)benzene;
bis-4-(N-carbazolyl)phenyl)phenylphosphine oxide;
2,7-bis-(diphenylphosphoryl)-9-(4-diphenylamino)phenyl-9'-phenyl-fluorene-
; di(4-(6H-indolo[3,2-b]quinoxalin-6-yl)phenyl)-diphenylsilane;
di(4-(6H-indolo[3,2-b]quinoxalin-6-yl)phenyl)-diphenylmethane;
bis[3,5-di(9H-carbazol-9-yl)phenyl]diphenylsilane;
2,6,14-tris(carbazol-9-yl)triptycene; 2,6,14-tris(diphenylphosphine
oxide)triptycene; 2,6,14-tris(diphenylamino)triptycene;
2,7-bis(diphenylphosphoryl)-9-phenyl-9H-carbazole;
tris[4-(9-phenylfluoren-9-yl)phenyl]aminobiphenyl-3-amine);
2,7-bis-(diphenylphosphoryl)spiro[fluorene-7,11'-benzofluorene].
[0066] In one embodiment of the process, the heavy main group metal
may comprise Bi. Bismuth has been found to be particularly suitable
because of its economic and process technology properties. There
exists a multitude of complexes which can be processed particularly
efficiently with organic fluorescent emitters in the context of wet
or gas phase processes. Even though bismuth follows directly after
lead in the Periodic Table, it has quite different physiological
properties. As a result of the fact that it can be absorbed only
with difficulty via the gastrointestinal tract, bismuth poisoning
is comparatively rare. On the contrary, salts of bismuth are used
in medicine for treatment of stomach ulcers or syphilis. It has
also been used as a contrast agent for x-ray examinations. The only
naturally occurring isotope of bismuth is that of mass 209. It is a
radioactive a emitter with a half-life of 1.9.times.10.sup.19
years. The long half-life results in an activity of 0.0033 Bq for 1
kg. This is therefore about 10 million times less than that of the
potassium which occurs in organisms. 1 kg of potassium by nature
contains 0.012%, i.e. 0.12 g, of the radioactive isotope .sup.40K
having a half-life t.sub.1/2 of 1.248.times.10.sup.9
years=39.38.times.10.sup.15 seconds, and has an atomic mass of
39.96. This results in a radioactivity of 31 825 Bq. Thus, the
radioactivity of bismuth for practical applications is negligibly
small and would not even be detectable by a human holding a Geiger
counter. Bismuth, in contrast to iridium (3/2) and europium (5/2),
has a nuclear spin of (9/2). This is capable of coupling with
unpaired electrons present on ligands (see also "Synthesen und
Eigenschaften neuer Tris(fluorphenyl)antimon- und
-bismut-Verbindungen. Kristallstruktur von
Tkis(2,6-difluorphenyl)bismuth" [Synthesis and Properties of Novel
Tris(fluorophenyl)antimony and -bismuth Compounds. Crystal
structure of Tkis(2,6-difluorophenyl)-bismuth] by T. Lewe et al.,
Z. anorg. allg. Chem. 622 (1996) 2009-2015). These properties and
the fact that bismuth deposits, in contrast to iridium deposits,
are subject to virtually no restriction may lead to a dramatically
better reactant cost situation.
[0067] Preferably, the bismuth complexes usable may include bismuth
in oxidation number of +II, +III or +V. These oxidation numbers
have been found to be particularly suitable as an addition point
for still further ligands, for example the organic emitter F. The
addition kinetics of the organic emitters with these oxidation
numbers of bismuth seem to be particularly suitable specifically
for a gas phase deposition as well. In addition, the bismuth
II/III/V complexes can be formed to layers very efficiently by
means of gas phase deposition or else wet processes on the basis of
their physical data, for example the evaporation temperature or
solubility.
[0068] More particularly, the coordination sphere of the Bi metal
atom can be altered by an addition of heteroatoms of a fluorescent
emitter. This may result in addition compounds in which specific
metal-heteroatom distances have been found to be particularly
advantageous. In the case of fluorescent emitters which can
interact with the Bi heavy metal atom via an oxygen, a preparation
which has been found to be particularly suitable is one in which
the Bi--O distance is not less than 2.25 .ANG. and less than 2.75
.ANG., preferably not less than 2.3 .ANG. and less than 2.70 .ANG.
and further preferably not less than 2.4 .ANG. and less than 2.6
.ANG..
[0069] In the case of interaction via a Cl heteroatom, a
preparation which has been found to be particularly suitable is one
in which the Bi--Cl distance is not less than 2.3 .ANG. and less
than 2.9 .ANG., preferably not less than 2.4 .ANG. and less than
2.80 .ANG. and further preferably not less than 2.45 .ANG. and less
than 2.75 .ANG..
[0070] In the case of interaction via an N heteroatom, a
preparation which has been found to be particularly suitable is one
in which the Bi--N distance is not less than 2.3 .ANG. and less
than 2.9 .ANG., preferably not less than 2.4 .ANG. and less than
2.80 .ANG. and further preferably not less than 2.45 .ANG. and less
than 2.70 .ANG..
[0071] In the case of interaction via an I heteroatom, a
preparation which has been found to be particularly suitable is one
in which the Bi--I distance is not less than 2.6 .ANG. and less
than 3.2 .ANG., preferably not less than 2.7 .ANG. and less than
3.10 .ANG. and further preferably not less than 2.8 .ANG. and less
than 3.1 .ANG..
[0072] In the case of interaction via a Br heteroatom, a
preparation which has been found to be particularly suitable is one
in which the Bi--Br distance is not less than 2.5 .ANG. and less
than 3.1 .ANG., preferably not less than 2.6 .ANG. and less than
3.0 .ANG. and further preferably not less than 2.7 .ANG. and less
than 2.95 .ANG..
[0073] The bond lengths may be determined from single-crystal data
of the compounds in question by methods known to those skilled in
the art.
[0074] These distances of the heteroatom-containing emitters from
the heavy metal atom show a sufficient heavy metal atom effect to
open up the fluorescence channel in the organic emitter and
additionally enable good interaction of the organic emitter with
the remaining ligands.
[0075] In a further configuration of the process, the proportion of
phosphorescent emission caused by electronic inter- and
intra-ligand transitions with purely electronic excitation may be
not less than 20% and not more than 100%. The incorporation of the
fluorescent emitter into the coordination sphere of the heavy metal
atom may open up an effective "phosphorescence channel" of the
organic emitter. In addition to fluorescent emission, additional
contributions can also be obtained through phosphorescent
radiation. This can contribute to a distinct increase in the
internal quantum yield of the layer. The distinction of whether a
radiation component is of fluorescent or phosphorescent origin can
be determined on the basis of time-correlated single photon
counting (TCSPC measurements). By means of TCSPC, the lifespan of
every single photon is measured and the distribution of the
lifespans is accumulated. Components on a microsecond timescale can
be attributed here to phosphorescent transitions, and faster
transitions to fluorescent transitions. What is considered in each
case is the mathematical fit to the intensity curve measured. This
method is known to those skilled in the art. Examples thereof can
be found in the experimental section.
[0076] In an additional configuration of the process, the organic
fluorescent emitters F may be selected from the group of the
substituted or unsubstituted C6-C60 aromatics or heteroaromatics.
To obtain a maximum phosphorescence contribution of the organic
fluorescent emitter and a very stable association of the emitter
with the heavy main group metal, it is particularly advantageously
possible to use fluorescent emitters within this size range. In
addition, it is possible to deposit these emitters efficiently
either from the liquid phase or from the gas phase. The individual
molecules may either have full aromatic through-conjugation or have
some nonaromatic sections.
[0077] In an alternative configuration of the process, the longest
lifetime of electronically excited states of the organic
fluorescent emitter F after incorporation into the coordination
sphere of the heavy main group metal M at room temperature may be
not less than 0.01 microsecond and not more than 10 000
microseconds. The incorporation of the organic fluorescent emitter
F into the coordination sphere of the heavy main group metal M may,
as a result of the spin-orbit coupling of the metal with the
excited electrons of the organic emitter, enable intercombination
of the singlet states with the triplet states. These can "open up"
the phosphorescence channel of the emitter, which can lead to a
higher quantum yield and longer observable lifetimes of the excited
electronic states of the emitter. The lifetimes can be determined
by standard methods, as conducted, for example, in the examples by
means of TCSPC. The fluorescent transitions feature lifetimes of
10.sup.-9-10.sup.-7 seconds, whereas the phosphorescent transitions
typically have longer time constants. Depending on the composition
of the electrical layer, it is also possible for several time
constants or lifetimes to be present. The longest lifetime in the
sense of the invention is that which has the greatest lifetime with
a proportion of the total lifetime of not less than 2.5%.
[0078] In a further configuration of the process, the organic
fluorescent emitters F may be selected from the group comprising
4,7-di(9H-carbazol-9-yl)-1,10-phenanthroline,
2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine,
3,5-bis(3-(9H-carbazol-9-yl)phenyl)pyridine,
2,8-di(9H-carbazol-9-yl)-dibenzo[b,d]thiophene,
2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole),
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole,
2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline,
8-hydroxyquinolinolatolithium,
4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole,
1,3-bis[2-(2,2'-bipyridin-6-yl)-1,3,4-oxadiazo-5-yl]benzene,
4,7-diphenyl-1,10-phenanthroline,
3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole,
bis(2-methyl-8-quinolinolato)-4-(phenyl-phenolato)aluminum,
6,6'-bis[5-(biphenyl-4-yl)-1,3,4-oxadiazol-2-yl]-2,2'-bipyridyl,
2-phenyl-9,10-di(naphthalen-2-yl)-anthracene,
2,7-bis[2-(2,2'-bipyridin-6-yl)-1,3,4-oxadiazol-5-yl]-9,9-dimethylfluoren-
e, 1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl]benzene,
2-(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline,
2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline,
tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane,
1-methyl-2-(4-(naphthalen-2-yl)-phenyl)-1H-imidazo[4,5-f][1,10]phenanthro-
line, 1,3-bis-(carbazol-9-yl)benzene,
1,3-bis(carbazol-9-yl)pyridine, 1,3,5-tris(carbazol-9-yl)benzene,
9-(3-(9H-carbazol-9-yl)phenyl)-3-(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)ph-
enyl)-9H-carbazole, 2,6,14-tris(carbazol-9-yl)triptycene,
1,3-bis(carbazol-9-yl)-benzene, 1,3,5-tris(carbazol-9-yl)benzene,
3,5-di(9H-carbazol-9-yl)biphenyl,
9-(3,5-bis(diphenylphosphoryl)phenyl)-9H-carbazole,
bis[3,5-di(9H-carbazol-9-yl)phenyl]diphenylsilane,
2,8-bis(diphenylphosphoryl)dibenzo[b,d]thiophene,
poly[3-(carbazol-9-yl)-9-(3-methyloxetan-3-ylmethyl)carbazole],
poly[3-(carbazol-9-ylmethyl)-3-methyloxetane]. These compounds have
been found, but without restriction, to be particularly suitable
for use as organic fluorescent emitters F. Both the electronic and
steric properties of these compounds allow sufficient interactions
with the heavy main group metals to "open up" the phosphorescence
channel with good internal quantum yields and long lifetime of the
layers. In addition, these compounds have sufficiently large
aromatic regions which can lead to suitable emission wavelengths.
The good interaction of the organic fluorescent emitters F can very
probably also be attributed to the steric features thereof and here
especially to the suitable coordination sites to the metal
atom.
[0079] In addition, these compounds have good processing in wet
processes and also gas phase deposition processes.
[0080] In a further configuration of the process, the organic
fluorescent emitter F may be
4,7-di(9H-carbazol-1-yl)-1,10-phenanthroline (BUPH1). BUPH1 shows,
very probably because of its electronic HOMO/LUMO structure, only
pure fluorescence emission at room temperature without coordination
to a heavy main group metal from the above-specified group. After
coordination or adduct formation with the main group metal,
phosphorescent emissions are observable with high quantum yields.
These are determined to a high degree by the electronic structure
of the organic emitter and the remaining ligands of the complex.
Layers having this emitter structure have been found to be
particularly efficient and long-lived. The long life can probably
be attributed to the size of the organic molecule and the low
crystallization tendency thereof.
[0081] In a further configuration of the process, the ligands of
the metal complex may independently be selected from the group
comprising halides and fluorinated or nonfluorinated C2-C20 alkyl
or aryl carboxylates, alkoxides, thiolates, cyanates, isocyanates,
thiocyanates, acetylacetonates, sulfonates. These ligands in the
metal complex may contribute to easy processibility in wet
processes and also gas phase processes, and because of their
coordination properties to the metal atom to simple alteration of
the coordination sphere of the metal atom. Within the metal
complex, it is possible here for only one or else more than one of
the abovementioned ligands to be present. Preferably, the complex
may have mixed ligands, either via extension of the coordination
sphere of the metal or via replacement of a single ligand or a
plurality of ligands. These ligands may additionally be utilized
for adjustment of the emission wavelength of the organic emitter.
This can be caused by electronic interactions of the ligand(s) with
the emitter. These ligands L in the metal complex may preferably
make up a portion of not less than 0% and not more than 20% of the
total emission yield of the layer. Preferably, this range may be
between not less than 0% and not more than 10% and additionally
preferably between not less than 0% and not more than 5%.
[0082] In addition, in a further aspect of the process, the ligands
L of the metal complex may independently be selected from the group
comprising C6-C30 aromatics and heteroaromatics.
[0083] These aromatics or heteroaromatics may contribute to easy
processibility in wet processes or else gas phase processes and
additionally enable the organic emitters to have simple
coordination to the metal atom. The interactions of the .pi.
electrons can additionally affect the position of the
phosphorescence wavelengths of the organic emitter and thus
contribute to an altered emission spectrum.
[0084] In a further embodiment, the metal complex may contain a
Bi(III) and at least one complex ligand from the group of the
unsubstituted, partly fluorinated or perfluorinated organic
carboxylic acids. Preferably, the metal complex may contain one,
two or three of these organic carboxylic acids. Organic carboxylic
acids may generally be selected from the group of these aliphatic
saturated monocarboxylic acids; aliphatic unsaturated
monocarboxylic acids; aliphatic saturated dicarboxylic acids;
aliphatic saturated tricarboxylic acids; aliphatic unsaturated
dicarboxylic acids; aromatic carboxylic acids; heterocyclic
carboxylic acids; aliphatic unsaturated cyclic monocarboxylic
acids. Particularly preferred partially fluorinated or
perfluorinated ligands L may be selected from substituted or
unsubstituted compounds of acetic acid, phenylacetic acid and/or
benzoic acid. More preferably, it is possible to use
nonfluorinated, partly fluorinated or perfluorinated acetic acid.
In a further preferred embodiment, one or more polydentate ligands
L in the unevaporated state may be disposed between the metal atoms
of the complex in a bridging manner. These compounds can be
processed in a simple manner either from the wet phase or via a gas
phase deposition process and enable good binding of the fluorescent
emitter within the layer. In this way, they can lead to long-lived
emitter components which have a very good quantum yield.
[0085] More preferably, the Bi(III) metal complexes as starting
materials, according to structures specified below, may either have
a mononuclear structure:
##STR00003##
or, according to structures specified below, a dinuclear
structure:
##STR00004##
where R.sup.1 and R.sup.2 may each independently be oxygen, sulfur,
selenium, NH or NR.sup.4 where R.sup.4 is selected from the group
comprising alkyl or aryl and may be bonded to R.sup.3; and R.sup.3
is selected from the group comprising alkyl, long-chain alkyl,
alkoxy, long-chain alkoxy, cycloalkyl, haloalkyl, aryl, arylene,
haloaryl, heteroaryl, heteroarylene, heterocyclo-alkylene,
heterocycloalkyl, haloheteroaryl, alkenyl, haloalkenyl, alkynyl,
haloalkynyl, ketoaryl, haloketoaryl, ketoheteroaryl, ketoalkyl,
haloketoalkyl, ketoalkenyl, haloketoalkenyl, where, in the case of
suitable radicals, one or more nonadjacent CH.sub.2 groups may
independently be replaced by --O--, --S--, --NH--, --NR.sup.o--,
--SiR.sup.oR.sup.oo--, --CO--, --COO--, --OCO, --OCO--O--,
--SO.sub.2--, --S--CO--, --CO--S--, --CY1=CY2 or --C.ident.C--, in
such a way that no O and/or S atoms are bonded directly to one
another, and likewise optionally by aryl or heteroaryl preferably
containing 1 to 30 carbon atoms (terminal CH.sub.3 groups are
understood as CH.sub.2 groups in the sense of CH.sub.2--H).
[0086] Without being bound by the theory, there is terminal
coordination of the metal via the ligand(s) in the case of the
mononuclear complexes. In the case of a bidentate complex, there is
di- or tridentate coordination of the metal atom. This coordination
geometry can facilitate the access of a fluorescent emitter and
thus contribute to effective complex or adduct formation. In
addition, these compounds in layers exhibit good electrical
properties and a low tendency to crystallization, and so high
quantum yields may be obtainable in a long-lived system.
[0087] In a further characteristic feature of the process, the
metal complex may comprise one or more compounds from the group of
trisarylbismuth(III) biscarboxylate and Bi(III) triscarboxylate.
Trisarylbismuth carboxylate is of the following formula:
##STR00005##
where Ar.sub.1, Ar.sub.2 and Ar.sub.3 are independently substituted
or unsubstituted, fluorinated or nonfluorinated aromatics or
heteroaromatics. These compounds can be processed particularly
easily by means of wet phase or gas phase deposition and enable
good coordination of the organic fluorescent emitters to the
central bismuth atom. The layers thus obtained feature a high
quantum yield and a low tendency to crystallization.
[0088] This can increase the lifetime of the layers.
[0089] In addition, in a further aspect of the process, the metal
complex may comprise one or more compounds from the group of partly
or fully fluorinated triphenylbismuth(V) bis(fluoro-benzoate) and
Bi(III) pentafluorobenzoate. These compounds can be processed
particularly easily by means of wet phase or gas phase deposition
and enable good coordination of the organic fluorescent emitters to
the central bismuth atom. The layers thus obtained feature a high
quantum yield and a low tendency to crystallization. This can
increase the lifetime of the layers.
[0090] In an additional characteristic feature of the process, the
metal complex may comprise one or more compounds from the group of
Bi(III) fluorobenzoate, Bi(III) fluoroalkylbenzoate, Bi(III)
fluorodialkylbenzoate, Bi(III) fluorotrialkylbenzoate, Bi(III)
pentafluorobenzoate and Bi(III) 3,5-trifluoromethylbenzoate. These
compounds having Bi in the III oxidation state and benzoate
substituents can be processed particularly easily by means of wet
phase or gas phase deposition and enable good coordination of the
organic fluorescent emitters to the central bismuth atom. The
layers thus obtained feature a high quantum yield and a low
tendency to crystallization. This can increase the lifetime of the
layers. The fluorination may cover either only one individual
hydrogen atom or extend as far as perfluorination of the compound.
The alkyl groups may preferably be C1-C5-alkyl and, if otherwise
specified, 1-4 positions of the base structure may independently be
alkylated.
[0091] In a further aspect of the process, the metal complex may
comprise one or more compounds from the group of the
trisarylbismuth(V) carboxylates. These compounds having Bi in the V
oxidation state can be processed particularly easily by means of
wet phase or gas phase deposition and enable good coordination of
the organic fluorescent emitters to the central bismuth atom. The
layers thus obtained feature a high quantum yield and a low
tendency to crystallization. This can increase the lifetime of the
layers. The fluorination may cover either only one individual
hydrogen atom or extend as far as perfluorination of the compound.
A preferred compound of this class of compounds is, for example,
wholly or partly fluorinated triphenylbismuth(V)
bis(fluorobenzoate).
[0092] In a further embodiment, the metal complex may be selected
from the group comprising Bi(III) triscarboxylate, Bi(III)
fluoroacetate and Bi(III) trifluoroacetate. Specifically the
coordination of the ligands via two oxygen atoms to the heavy main
group metal may enable easier alteration of the coordination sphere
via the entry of the organic fluorescence emitter. By virtue of
this configuration, it is possible to produce particularly stable
and efficient layers having long lifetimes.
[0093] In an additional configuration of the process, the metal
complex and the organic fluorescent emitter F may be deposited on a
carrier substrate by means of coevaporation, rotary or curtain
coating, bar coating or printing. More preferably, the amorphous
layer may be produced by means of gas phase deposition or wet
processes. By means of these processes, it is possible to deposit
the metal complex and the organic fluorescence emitter together and
thus to form the amorphous layer. Both substances can be sublimed
from different sources using thermal energy in a coevaporation
process. By means of these processes, particularly homogeneous and
uniform layers are obtained. Solvent processes may preferably be
conducted in such a way that the components are deposited onto a
substrate from a solvent. This can simplify the process regime and
enable less expensive production. In addition, still further
materials, for example matrix materials which do not coordinate to
the metal atom, may be dissolved in the solvent and/or deposited as
well within the layer. It is likewise possible for these matrix
materials to be additionally evaporated as well from further
sources.
[0094] In a further characteristic feature of the process, the
molar ratio of metal complex to organic fluorescent emitter F may
be not less than 1:10 and not more than 10:1. These ratios of metal
complex to organic emitter within the layer have been found to be
particularly advantageous for obtaining high luminances and a long
lifetime of the layers. Higher proportions of metal complex can
lead to an increase in the phosphorescence yield as a result of the
change in layer conductivity, but this effect can also be achieved
by other compounds with lower material costs. Lower proportions of
metal complex, in contrast, can lead to only inadequate activation
of the phosphorescence pathway. This may be disadvantageous for the
internal quantum yield of the layer. Preferably, the molar ratio of
metal complex to organic fluorescent emitter F is not less than 1:5
to 5:1 and additionally preferably 1:3 to 3:1.
[0095] In addition, the deposition of the metal complex and the
organic fluorescent emitter F can be effected by means of a
coevaporation process, and the deposition rate of the organic
electronic layer may be not less than 0.1 .ANG./s and not more than
200 .ANG./s. The opening-up of the phosphorescence channel of the
organic emitter is essentially coupled to the change in
coordination of the heavy main group metal M as a result of the
incorporation of or adduct formation with the organic emitter. The
spatial proximity of the emitter to the metal enables spin-orbit
coupling which leads to a reduced lifetime of excited triplet
states of the organic emitter. It has been found that,
surprisingly, these distances between emitter and metal can also be
brought about by means of coevaporation. This is surprising because
a prerequisite for the existence of high quantum yields would be
expected to be a very well-defined separation, as, for example, in
single crystals or in crystalline structures. However, this cannot
be expected in the case of production by means of coevaporation,
since the individual molecules are deposited in an unordered,
amorphous manner within a layer. This process makes it possible to
obtain solvent-free layers having a long lifetime. The preferred
deposition rate may contribute to a homogeneous layer structure.
Smaller deposition rates are not in accordance with the invention,
since these would make the production much more expensive because
of the time taken. Higher rates are additionally not in accordance
with the invention since the quantum yield can be decreased because
of inadequate establishment of the distance between metal and
organic emitter. Preferably, the deposition rate may additionally
be not less than 0.1 .ANG./s and not more than 150 .ANG./s and
additionally preferably not less than 1.0 .ANG./s and not more than
100 .ANG./s.
[0096] Some embodiments provide a layer in an organic electronic
component produced by the process of the invention. By means of the
process of the invention, it is possible to produce layers in
organic electronic components that are suitable for emission and
conversion of light. The layers may have a layer thickness of not
less than 1 nm and not more than 500 .mu.m and be applied by means
of the above-described processes. In the course of coevaporation
processes, the layer is obtained by the direct application of the
substances from the gas phase, whereas in wet processes the layer
is obtained after evaporation of the solvent(s).
[0097] In addition, the layer of the invention may find use as an
active layer in an organic electrical component for conversion of
electrical current to light, of light to electrical current and of
light to light of another wavelength. The layer of the invention
can accordingly be utilized for generation of power by absorption
of light waves, and also for production of light by means of an
electrical current. In addition, the layer can also be utilized for
conversion of light waves to light waves of another wavelength, for
example by absorption of light quanta and release of light quanta
of another wavelength.
[0098] Other embodiments provide an organic semiconductor component
selected from the group comprising photodiodes, solar cells,
organic light-emitting diodes, light-emitting electrochemical cells
comprising the layer of the invention. The process described and
the layers producible thereby may correspondingly find use for
absorbent components such as photodiodes or solar cells. In
addition, the layers may also be used for photo-conversion layers
in photovoltaics or sensors. The process is compatible with the
standard production steps for these components and it is possible
in this way to inexpensively obtain long-lived and efficient
components.
[0099] With regard to further features and advantages of the
above-described organic semiconductor components, reference is
hereby made explicitly to the elucidations in connection with the
layer of the invention and the process of the invention. Also,
features of the invention and advantages of the process of the
invention should also be applicable and be considered to be
disclosed for the layers of the invention and the organic
semiconductor components of the invention, and vice versa. The
invention also includes all combinations of at least two features
disclosed in the description and/or the claims.
Examples
[0100] Within the process of the invention, an organic fluorescence
emitter is made capable of phosphorescence-based emission or
absorption of light by interaction with a heavy main group metal
(In, Tl, Sn, Pb, Sb, Bi) within a layer or in solution. To
illustrate the principle, compounds having the main group metals
Bi, Pb and Sn are presented.
[0101] The organic fluorescence emitter used is
4,7-di(9H-carbazol-9-yl)-1,10-phenanthroline (BUPH1).
Characterization of the Organic Fluorescence Emitter
[0102] BUPH1 is an uncharged, neutral organic molecule of the
following structure:
##STR00006##
where an electron-transporting phenanthroline core is bonded to two
hole-transporting carbazole units. The compound is a bidentate
Lewis base and the two nitrogen atoms of the core, just like the
.pi. electron systems of the aromatics, can interact with charged
metals.
[0103] FIG. 3 shows the spectra of solid BUPH1 and of BUPH1
dissolved in tetrahydrofuran (THF). BUPH1 at room temperature shows
blue photoluminescence with a maximum emission of the solid
material at 420 nm and of the THF-dissolved compound at 425 nm. The
wavelength shift of 5 nm is caused by the polarity of the solvent
chosen.
[0104] FIG. 4 shows the photoluminescence spectrum of BUPH1 in
2-methyl-THF at 77 K. The compound shows 5 emission maxima at 410,
475, 510, 550 and 600 nm. Because of the fact that the maxima at
475, 510, 550 and 600 nm are well below that at 410 nm, it can be
concluded that these emissions are from the triplet state and
consequently originate from phosphorescence transitions
(T1.fwdarw.S0). In general, this quantum yield is lower, since this
transition is spin-forbidden. In addition, the Stokes shift of the
emissions at 475, 510, 550 and 600 nm also suggests the presence of
a phosphorescence transition of the BUPH1 at low temperatures.
Phosphorescent transitions, compared to fluorescence transitions,
are always lower in energy. In addition, the fact that the 475,
510, 550 and 600 nm emissions are absent at room temperature also
suggests the presence of triplet emissions. It follows from this
that the first emission maximum can be attributed to a fluorescence
transition and the further transitions to phosphorescence
transitions. The energy of the triplet transition is astonishingly
very high at 2.6 eV (475 nm) compared to other Lewis bases.
[0105] The photoluminescence quantum yield (PLQY) of BUPH1 was
determined in THF solution. The PLQY of a fluorophore (emitter)
indicates the ratio between the number of photons emitted and
absorbed. A method of calculation is given, for example, in Albert
M. Brouwer, Pure Appl. Chem., vol. 83, no. 12, pp. 2213-2228, 2011.
The BUPH1 PLQY in THF, using 9,10-diphenyl-anthracene in
cyclohexane as reference, is 29.8%.
[0106] FIG. 5 shows the time-correlated single photon counting
(TCSPC) spectrum of BUPH1 in THF for determination of the
fluorescence lifetime. The figure shows the exponential drop in
photoluminescence as a function of time. The experiment was
conducted in an inert atmosphere with .lamda..sub.ex 295 nm,
.lamda..sub.em 420 nm and TAC 50 ns. The TAC ("time to amplitude",
time/amplitude converter) is a part of the TCSPC spectrometer which
produces an output signal having an amplitude proportional to the
time interval between input "start" and "stop" pulses. The
amplitude distribution of the output pulses is then recorded by a
multichannel analyzer. It is thus a measure of the distribution of
the time intervals between the start and stop pulses and is often
referred to as "time spectrum". The data can be fitted with a
single exponential function, which results in a lifetime of
7.06*10.sup.-9 s for BUPH1 in THF at room temperature (CHISQ=1.14).
This means that the lifetime of the excited state at room
temperature lies on a nanosecond scale, which corresponds to a
fluorescence transition, having a typical lifetime of 10.sup.-9 up
to 10.sup.-7 s.
[0107] FIG. 6 shows the cyclic voltammogram of BUPH1 in
acetonitrile. The measurement was recorded with Pt/Pt electrodes
against an Ag/AgCl reference electrode at a rate of 20 mV/s. The
energy of the HOMO level can be calculated from the oxidation
potential of BUPH1 (to BUPH11 of 1.43 V. A HOMO level of BUPH1 of
5.82 eV is obtained.
A. Examples Using the Heavy Main Group Metal Bi
I. Characterization of the Metal Complexes Used
[0108] FIG. 7 shows the UV absorption spectra of Bi(tfa).sub.3,
Bi(pFBz).sub.3 and Bi(3,5tfmBz).sub.3. The structural formulae of
the compounds are shown further down.
##STR00007##
[0109] The individual spectra show a strong n-.pi.* and .pi.-.pi.*
absorption which can be attributed to the carboxylate ligands and
the central bismuth atom. The bismuth carboxylates absorb light
only in the UV region of the spectrum, which is why they have the
appearance of white solids. The graph inserted shows a Tauc plot
with which the optical band gap of the individual compounds can be
determined. The graphs show a linear regime which marks the
starting point of the absorption. If this linear regime is
extrapolated to the abscissa, the energy of the optical band gap is
obtained. For Bi(tfa).sub.3, Bi(pFBz).sub.3 and Bi(3,5tfmBz).sub.3,
a relatively large band gap in the region of 4.46, 4.32 and 4.34 eV
is obtained. This shows that the bismuth carboxylates exhibit
insulator properties.
[0110] FIG. 8 shows the plot of the molar extinction coefficients
of Bi(tfa).sub.3, Bi(pFBz).sub.3 and Bi(3,5tfmBz).sub.3 in THF
against wavelength. At 265 nm, the extinction coefficients for
Bi(tfa).sub.3, Bi(pFBz).sub.3 and Bi(3,5tfmBz).sub.3 are 243, 3065
and 2200 Lmol.sup.-1 cm.sup.-1. In the case of Bi(pFBz).sub.3 and
of Bi(3,5tfmBz).sub.3, the n-.pi.* and .pi.-.pi.* transitions are
allowed, which leads to extinction coefficients exceeding 1000
Lmol.sup.-1 cm.sup.-1.
II. Production of the Layers
[0111] A prefabricated quartz substrate is treated by means of an
oxygen plasma for 10 minutes and transferred as quickly as possible
to an evaporator within an argon-filled glovebox having a water
content less than 2 ppm.
[0112] The thermal evaporation is effected at a base pressure less
than 2.times.10.sup.-6 mbar, which is maintained over the entire
vapor deposition step.
[0113] The metal complex and the organic emitter are simultaneously
heated up to a temperature just below the evaporation point
thereof. Subsequently, the metal complex is heated further until a
constant evaporation rate is achieved. The same procedure is
followed with the organic emitter and, with mutually constant
evaporation rates, the evaporator slide valve is opened.
[0114] The deposition rate of the two substances is set to 1
.ANG./s, the concentration of the bismuth complex being regulated
as a function of the desired Bi:BUPH1 ratio; for example, a
concentration of 50% is achieved with a BUPH1 deposition rate of
0.5 .ANG./s and a Bi deposition rate of 0.5 .ANG./s. This
corresponds to a ratio of 1:1.
[0115] After the vapor deposition, the two sources are cooled down
to below 40.degree. C. and the evaporator is flooded with dry
argon.
[0116] A series of Bi:BUPH1 films with different composition was
produced via the above-described coevaporation method. Thus, 200
nm-thick Bi:BUPH1 films were deposited as emitter layers on a piece
of quartz glass. The following ratios were established (the
abbreviation of bismuth(III) trifluoroacetate is Bi(tfa).sub.3 and
that of Bi(III) pentafluorobenzoate is Bi(pFBz).sub.3):
TABLE-US-00001 Compound Ratio Bi(tfa).sub.3:BUPH1 1:1
Bi(tfa).sub.3:BUPH1 1:2 Bi(tfa).sub.3:BUPH1 1:3 Bi(tfa).sub.3:BUPH1
1:4 Bi(tfa).sub.3:BUPH1 0:1 Bi(tfa).sub.3:BUPH1 3:1
Bi(pFBz).sub.3:BUPH1 1:1 Bi(pFBz).sub.3:BUPH1 1:2
Bi(pFBz).sub.3:BUPH1 1:3
III. Characterization of the Layers Produced by Coevaporation
III.a UV Absorption
[0117] FIG. 9 shows the UV absorption spectra of BUPH1,
Bi(tfa).sub.3, and Bi(tfa).sub.3:BUPH1 layers produced by
coevaporation with different deposition rates. The layer thickness
is 200 nm. Two main absorption bands are visible for the films. The
dominant absorption band lies between 230-350 nm and can be
assigned to a spin-allowed .pi.-.pi.* transition in BUPH1. Compared
to the pure BUPH1 film, the n-.pi.* transition of BUPH1 at 335 nm
is absent in the composite layers (metal+emitter). This indicates
coordination of the free nitrogen electron pairs to the bismuth. It
follows from this that BUPH1 interacts with the bismuth to form an
adduct or complex. In addition, the absorption spectrum of the
composite films shows a low-lying absorption band at 350 nm-500 nm,
which extends into the visible range. This band can probably be
assigned to an intra-ligand charge transfer.
[0118] FIG. 10 shows the UV absorption spectra of BUPH1 and of
Bi(pFBz).sub.3:BUPH1 layers produced by coevaporation with
different deposition rates. The layer thickness in each case is 200
nm. Compared to the pure BUPH1 film, the n-.pi.* transition of
BUPH1 at 335 nm is absent in the composite layers. This indicates
coordination of the free nitrogen electron pair to the bismuth. It
follows from this that BUPH1 binds/coordinates to the bismuth to
form an adduct or complex. In addition, the absorption spectrum of
the composite films shows a low-lying absorption band at 350 nm-500
nm, which extends into the visible range. This band can probably be
assigned to an intra-ligand charge transfer.
III.b Photoluminescence
[0119] FIG. 11 shows the normalized photoluminescence spectra of
BUPH1 and of Bi(tfa).sub.3:BUPH1 layers produced by coevaporation
with different deposition rates. The layer thickness in each case
was 200 nm. The emission spectra are normalized to the maximum
intensity of the BUPH1 film. The emission maximum for BUPH1 is at
420 nm and for the composite layers at 585 nm. BUPH1 film
.lamda..sub.ex: 365 nm, .lamda..sub.em: 420 nm;
Bi(tfa).sub.3:BUPH1=1:1 .lamda..sub.ex: 410 nm, .lamda..sub.em: 585
nm; Bi(tfa).sub.3:BUPH1=1:2 .lamda..sub.ex: 410 nm, .lamda..sub.em:
580 nm; Bi(tfa).sub.3:BUPH1=1:3 .lamda..sub.ex: 410 nm,
.lamda..sub.em: 585 nm; Bi(tfa).sub.3:BUPH1=1:4 .lamda..sub.ex: 410
nm, .lamda..sub.em: 585 nm; Bi(tfa).sub.3:BUPH1=3:1 .lamda..sub.ex:
410 nm, .lamda..sub.em: 585 nm. Compared to the low-temperature
emission spectrum of BUPH1, which had emission maxima at 520, 550
and 560 nm, the adduct or addition complex shows only one broad
phosphorescence emission band at room temperature.
[0120] FIG. 12 shows the normalized photoluminescence spectra of
BUPH1 and of Bi(pFBz).sub.3:BUPH1 layers produced by coevaporation
with different deposition rates. The layer thickness in each case
is 200 nm. BUPH1 .lamda..sub.ex: 335 nm, .lamda..sub.em: 420 nm;
Bi(pFBz).sub.3:BUPH1=1:1 .lamda..sub.ex: 395 nm, .lamda..sub.em:
535 nm; Bi(pFBz).sub.3:BUPH1=1:2 .lamda..sub.ex: 395 nm,
.lamda..sub.em: 542 nm; Bi(pFBz).sub.3:BUPH1=1:3 .lamda..sub.ex:
395 nm, .lamda..sub.em: 540 nm. The composite layers show a maximum
emission at 550 nm. By comparison with FIG. 11, it is found that
the emission at higher wavelengths is different between the
different Bi complexes. This is probably because of the fact that
the metal ligands (trifluoroacetate or pentafluoroacetate) can
affect the emission wavelengths of the Bi:BUPH1 adduct or complex
obtained. Compared to the low-temperature emission spectrum of
BUPH1, which had emission maxima at 520, 550 and 560 nm, the
complex shows only one broad phosphorescence emission band at room
temperature.
III.c Photoluminescence Quantum Yield (PLQY)
[0121] The photoluminescence quantum yield (PLQY) of composite
layers could not be determined in the solid state. For this reason,
the layers of Bi(tfa).sub.3:BUPH1=1:2 and Bi(pFBz).sub.3:BUPH1=1:2
were dissolved in dichloromethane and the PLQY was measured in
solution. The PLQY of Bi(tfa).sub.3:BUPH1=1:2 is 3.7% (Coumarin 153
in ethanol as reference). For Bi(pFBz).sub.3:BUPH1, the PLQY is 6%
(Coumarin 153 in ethanol as reference). These PLQY values are well
above the PLQYs of other bismuth complexes from the literature,
which are generally below 1%. One example is a PLQY of 0.2% for
dithienobismole, obtained according to WO 2011 111621 A1.
III.d Time-Correlated Single Photon Counting TCSPC
[0122] The Bi(tfa).sub.3:BUPH1 and Bi(pFBz).sub.3:BUPH1 films
deposited with different compositions were examined by means of
TCSPC (time-correlated single photon counting) measurements in an
inert atmosphere. At room temperature, the TCSPC measurement for
the Bi:BUPH1 films gives complex lifetimes in the microsecond
range. This is a clear pointer to the presence of a phosphorescence
transition. The results of the measurements on the individual films
are shown in the following tables:
The Results for the Bi(tfa).sub.3:BUPH1 Films
TABLE-US-00002 [0123] Film, 200 nm, 500 ns TAC range T1/s T2/s T3/s
Bi(tfa).sub.3:BUPH1 ratio *10.sup.-9 B1/% *10.sup.-8 B2/%
*10.sup.-7 B3/% 1:1 2.68 46.96 2.03 15.70 1.42 21.05 1:2 3.80 10.00
2.98 11.27 1.46 71.08 1:3 3.58 21.48 2.54 15.16 1.27 54.08 1:4 2.46
32.35 3.10 14.89 1.21 28.56
The Results for the Bi(pFBz).sub.3:BUPH1 Films
TABLE-US-00003 [0124] Film, 200 nm, 5 .mu.s TAC range
Bi(pFBz).sub.3:BUPH1 T1/s T2/s ratio *10.sup.-7 B1/% *10.sup.-6
B2/% 1:1 4.30 32.64 1.18 63.05 1:2 4.71 26.51 1.33 79.86 1:3 1.50
3.86 0.98 96.15
[0125] As can be seen from the graphs, it is apparent that the
radiative lifetime of the emitters in the Bi(tfa).sub.3:BUPH1 films
is somewhat shorter compared to the emitters in the
Bi(pFBz).sub.3:BUPH1 films. It appears that the use of
Bi(tfa).sub.3 leads to stronger spin-orbit coupling of the organic
emitter, which more strongly allows the phosphorescence transition
of BUPH1 in this complex in quantum-mechanical terms. This in turn
leads to a shorter radiative lifetime compared to Bi(pFBz).sub.3.
The Lewis acid character of Bi(tfa).sub.3 is higher compared to
Bi(pFBz).sub.3, which leads to enhanced interaction in this
example.
[0126] It should additionally be noted that the radiative lifetime
of the emitters in the Bi(tfa).sub.3:BUPH1 films was fitted by
means of a triexponential function, and that of the
Bi(pFBz).sub.3:BUPH1 films with a diexponential function. This may
indicate that a whole collection of molecules in the film is active
and is involved in the emission.
III.e XRD Spectrum
[0127] FIG. 13 shows the XRD spectrum of a Bi(tfa).sub.3:BUPH1
(1:1) film. The layer thickness of the Bi(tfa).sub.3:BUPH1 (1:1)
film is 2 .mu.m. The film generates only a broad halo over a wide 2
theta range in the x-ray diffractogram, which suggests an amorphous
arrangement of the metal complex-emitter compounds. This means that
the individual phosphorescent assemblies are arranged in an
irregular, amorphous manner in the layer. This may be attributable
to the fact that the compounds in the film are of mixed
stoichiometry, or that no long-range order can be established
between the individual emitter assemblies because of the
preparation methodology chosen.
B. Examples Using the Heavy Main Group Metal Sn
[0128] As a further example of emitters which contain a heavy main
group metal and have phosphorescence at room temperature, Sn
compounds are used. The metal starting material used was tin(II)
chloride (SnCl.sub.2). BUPH1 is an organic fluorescent emitter
which interacts with the heavy atom via weak electrostatic and/or
.pi. interactions. The influence of the heavy metal allows hitherto
spin-forbidden electronic transitions of BUPH1 in
quantum-mechanical terms, and a significant phosphorescence
contribution at room temperature is obtained. These results show
the suitability in principle of this class of compound for use in
layers of organic electrical components as well.
[0129] I. Preparation of Sn-BUPH1 composite solutions in THF
SnCl.sub.2 and BUPH1 are allowed to react in 3 mL of
tetrahydrofuran (THF) solution in a ratio of 1:1, 1:2 or 1:3, and
this solution is then analyzed spectroscopically. 5 .mu.L of
SnCl.sub.2 (10.sup.-2 M in THF) and 5 .mu.L of BUPH1 (10.sup.-2 M
in THF) in 3 mL of THF were used, in order to establish a molar
ratio of 1:1.
II. Characterization of the Solutions Prepared
II.a UV Absorption
[0130] FIG. 14 shows the UV absorption spectra of SnCl.sub.2-BUPH1
in THF in different molar ratios (1:1, 1:2 and 1:3). The absorption
bands in the composite THF solutions of SnCl.sub.2-BUPH1 between
250-375 nm are identical to the optical transitions of BUPH1 (cf.
FIG. 3) in this region. The increase in intensity of the absorption
bands of SnCl.sub.2-BUPH1 is proportional to the concentration of
BUPH1 in the solution. Interestingly, the absorption spectrum of
the composite THF solutions additionally shows a low-lying
absorption band in the range of 375-450 nm, which extends into the
visible range. This region is shown in enlarged form in FIG. 15.
This band can probably be assigned to an intra-ligand charge
transfer of the BUPH1-Sn adduct or addition complex formed.
II.b Photoluminescence
[0131] FIG. 16 shows the photoluminescence spectra of
SnCl.sub.2-BUPH1 in THF solution in a molar ratio of 1:1, 1:2 and
1:3. The excitation wavelength for the spectra was 410 nm, since
the intra-ligand charge transfer probably takes place at this
wavelength, which is found to be responsible for the
phosphorescence emission band. The composite THF solutions show a
maximum emission at 580 nm and the intensity of the bands barely
changes with the increase in the concentration of the BUPH1 in
solution. Without being bound by the theory, the emission is caused
mainly by BUPH1, which is made capable of phosphorescence because
of the effect of the heavy metal tin on the spin-forbidden
electronic transitions. Compared to the low-temperature emission
spectrum of BUPH1 (cf. FIG. 4), which has emission maxima at 520,
550 and 600 nm, the SnCl.sub.2-BUPH1 adduct or addition complex
shows a broad phosphorescence emission band at room
temperature.
II.c Time-Correlated Single Photon Counting TCSPC
[0132] The SnCl.sub.2-BUPH1 solutions prepared with different molar
ratios were examined by means of time-correlated single photon
counting measurements in an inert atmosphere (argon). At room
temperature, the TCSPC measurement for the SnCl.sub.2-BUPH1 adducts
or addition complexes gives lifetimes in the microsecond range
(ratio 1:1 in FIG. 17, 1:2 in FIG. 18 and 1:3 in FIG. 19). This is
a clear pointer to the presence of a phosphorescence transition.
The results of the measurements on the individual samples are shown
in the table below.
TABLE-US-00004 Molar SnCl.sub.2-BUPH1 ratio T1/.mu.s 1:1 0.84 1:2
1.12 1:3 0.76
[0133] The spectra were measured on a 5 .mu.s timescale, with
variation in the phosphorescence lifetime of the composite THF
solutions examined in the range from 0.76 to 1.12 .mu.s.
C. Examples Using the Heavy Main Group Metal Pb
[0134] As a further example of emitters which contain a heavy main
group metal and have phosphorescence at room temperature, Pb
compounds are used. These results show the suitability in principle
of this class of compound for use in layers of organic electrical
components as well.
I Preparation of Pb-BUPH1 Composite Solutions in THF
[0135] PbTFA (lead trifluoroacetate) and BUPH1 are allowed to react
in 3 mL of THF solution in a ratio of 1:1, 1:2 or 1:3 and the
solution is then analyzed spectroscopically. 5 .mu.L of PbTFA
(10.sup.-2 M in THF) and 5 .mu.L of BUPH1 (10.sup.-2 M in THF) in 3
mL of THF were used, in order to establish a molar ratio of
1:1.
II. Characterization of the Solutions Prepared
II.a UV Absorption
[0136] FIGS. 20 and 21 show the UV-VIS absorption spectra of
PbTFA-BUPH1 in THF in a molar ratio of 1:1, 1:2 and 1:3.
[0137] The absorption bands in the composite THF solutions of
PbTFA-BUPH1 between 250-375 nm are identical to the optical
transitions of BUPH1 in this region. The increase in intensity of
the absorption bands of PbTFA-BUPH1 is proportional to the
concentration of BUPH1 in the solution. Interestingly, the
absorption spectrum of the composite THF solutions additionally
shows a low-lying absorption band in the range of 375-415 nm (FIG.
21), which extends into the visible range. This band can probably
be assigned to an intra-ligand charge transfer of the BUPH1-Pb
adduct or addition complex formed.
II.b Photoluminescence
[0138] FIG. 22 shows the photoluminescence spectra of PbTFA-BUPH1
in THF solution in a molar ratio of 1:1, 1:2 and 1:3. The compounds
were excited with a wavelength of 410 nm, since the intra-ligand
charge transfer probably takes place at this wavelength, which is
found to be responsible for the phosphorescence emission band. The
composite THF solutions show a maximum emission at 536 nm and the
intensity of the bands barely changes with the increase in the
concentration of the BUPH1 in solution. Without being bound by the
theory, the emission is caused mainly by BUPH1, which is made
capable of phosphorescence because of the effect of the heavy metal
lead on the spin-forbidden electronic transitions. Compared to the
low-temperature emission spectrum of BUPH1 (see FIG. 3), which has
emission maxima at 520, 550 and 600 nm, the PbTFA-BUPH1 adduct or
addition complex shows a broad phosphorescence emission band at
room temperature.
II.c Time-Correlated Single Photon Counting TCSPC
[0139] The PbTFA-BUPH1 solutions prepared with different molar
ratios were examined by means of time-correlated single photon
counting measurements in an inert atmosphere (argon). At room
temperature, the TCSPC measurement for the PbTFA-BUPH1 adducts or
addition complexes gives lifetimes in the microsecond range (ratio
1:1 in FIG. 23, 1:2 in FIG. 24 and 1:3 in FIG. 25). This is a clear
pointer to the presence of a phosphorescence transition. The
results of the measurements on the individual samples are shown in
the table below.
TABLE-US-00005 Molar PbTFA:BUPH1 ratio T1/.mu.s 1:1 2.61 1:2 9.58
1:3 52.56
[0140] The spectra were measured on a 20 .mu.s timescale, with
variation in the phosphorescence lifetimes of the composite THF
solutions examined in the range from 2.61 to 52.56
microseconds.
[0141] Even though the invention has been illustrated in detail and
described by the preferred working example, the invention is not
restricted by the examples disclosed and other variations can be
derived therefrom by the person skilled in the art without leaving
the scope of protection of the invention.
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